Flock mating in sheep

Abstract

Romney rams were joined with Romney ewes in two experiments. When groups of two-tooth and six-tooth rams were joined with either 200 or 400 ewes, ram age had no effect on numbers of ewes mated. Fertility of ewes mated by rams of each age group was similar. In a second experiment groups of 4 two-tooth rams were compared with groups of 4 six-tooth rams when joined with either 240 or 720 ewes. Two-tooth rams each mated with a lower percentage of the total number of ewes in oestrus than did each of the six-tooth rams (P < 0.01). Fertility of ewes mated with rams of each age group was similar. During 8 h continuous observation sexual activity differed little between the ram age groups when run with 14 oestrous spayed ewes, but six-tooth rams were more active when run with 42 such ewes. In a 24 h period almost all of the 42 ewes were marked by both ram age groups, although two-tooth rams each marked a lower number of ewes than the six-tooth rams (20.4 v. 29.9 respectively. P < 0.01). Most rams were capable of at least 10 services in 8 h (range 0–30).